The present invention relates generally to vehicle wheel alignment systems utilizing optical sensors to acquire measurements of vehicle wheel alignment angles, and in particular, to a vehicle wheel alignment system configured to identify rolling movement of the at least one vehicle wheel during a vehicle wheel alignment procedure, or elevation changes of two or more vehicle wheels, which may adversely affect vehicle wheel alignment angle measurements.
Known vehicle wheel alignment systems utilizing optical sensors, i.e. machine vision, have been in use by the vehicle service industry for several years. A typical machine vision vehicle wheel alignment system, such as the Series 811 wheel alignment system, configured with the DSP600 sensors manufactured by Hunter Engineering Co. of Bridgeton, Mo. consists of a console unit, a set of cameras, and a set of optical targets. The console unit contains at least one central processor, such as a microprocessor, or a suitable set of logic circuits configured with image processing and vehicle wheel alignment software applications, and incorporates various operator interfaces, including a keyboard, a mouse, a printer, and a display device. The cameras are coupled to the computer, and the optical targets are each disposed within the field of view of at least one of the cameras, typically mounted to the wheels of a vehicle undergoing an alignment inspection. In some machine vision wheel alignment systems, optical targets are not used, and the cameras are configured to acquire images of identifiable features on the vehicle wheels, from which alignment angle measurements are determined.
The optical targets or identifiable features on the vehicle wheels are identified in images obtained by the optical sensors, and utilized to determine the position and orientation of the vehicle wheels. The image processing may take place in logic circuits associated with the optical sensors, in an interface computer, or in the console microprocessor. Once the position and orientation of each optical target or identifiable wheel feature is determined, the position and orientation of the associated vehicle wheel is identified, and correspondingly, the various vehicle wheel alignment angle measurements may be either determined or calculated. These angles typically include camber, caster, and toe angles for each vehicle wheel, the vehicle centerline, and the vehicle rear thrust line.
During vehicle wheel alignment procedures, it is often necessary for an operator to “lock” the vehicle brakes to ensure that the wheels of the vehicle do not roll during an alignment angle adjustment or measurement procedure. For example, it is particularly important that the steered wheels of a vehicle be prevented from rolling movement during a live caster angle adjustment procedure which requires a wheel to be adjusted about its Axis of Rotation (AR) to change live caster. It is also important that the steered wheels of a vehicle be prevented from rolling movement during a steering procedure where SAI is being measured and which requires steering the vehicle wheels from one side to another. To prevent the rear wheels from rolling during the steering procedure, the vehicle is typically positioned on a set of slip plates, which are selectively configured to permit a sliding motion of the vehicle in response to forces acting on the vehicle during a turning of the vehicle steered wheels.
Accordingly, it would be advantageous to provide a method for detecting if the vehicle wheels roll during vehicle wheel alignment angle measurements, or if the slip plates upon which the rear wheels are positioned are in a “locked” configuration, preventing required sliding motion of the vehicle during a steering procedure, and to provide an operator with a suitable warning.
Additionally, during vehicle wheel alignment procedures, it is often necessary for the operator to jack or elevate the wheels on an axle or common axis to complete a vehicle wheel alignment measurement procedure or to access alignment angle adjustment components. When an axle or vehicle suspension components are jacked or elevated, such that the vehicle wheels are no longer in contact with a supporting surface, the forces acting on the vehicle suspension system change, and correspondingly, measured vehicle wheel alignment angles change. Measurements of these alignment angles acquired with the vehicle wheels in an unsupported or jacked configuration may not be representative of the actual alignment angles when the vehicle wheel is resting on a supporting surface, and accordingly, should not be utilized in wheel alignment procedures. Furthermore, some vehicle wheel alignment angle measurement procedures cannot be completed with a vehicle wheel in an unsupported or jacked configuration.
Accordingly, it would be advantageous to provide a vehicle wheel alignment system with a method for detecting changes in the elevation of vehicle wheels, so as to enable detection of a wheel jacking procedure or vehicle lift elevation change, and to enable or disable corresponding procedures and measurements in a vehicle wheel alignment software application.